1. Technical Field of the Invention
The present invention relates to a tape cassette, and more particularly, to a resilient member for biasing a locking plate which is used to lock a front cover of such a tape cassette.
2. Prior Art
In general, a tape cassette 1 for containing a video or audio tape or a cleaning tape is, as shown in FIG. 1, composed of an upper ease 2, a lower ease 3 and a front cover or lid 4 pivotally mounted at its lateral plates to lateral sides of the front of the cassette 1 for protecting the tape exposed to the air at the front end of the cassette.
Usually, the front cover 4 doses the front end of the cassette as shown in FIG. 1 when the tape cassette is removed from a video deck or a tape recorder. Referring to FIGS. 3-6 which are enlarged views of the portion A of FIG. 1 as applied to the conventional tape cassette, FIG. 3 is an enlarged plane view of the lower ease, FIG. 4 is a cross sectional view taken along the line IV--IV of FIG. 3, FIG. 5 is a spring used in the conventional cassette and FIG. 6 is a left side view of the cassette. As shown, a locking paw 6 supported by a locking plate 7 engages a recess (not shown) formed on the inner face of one of the lateral plates of the front cover 4 so as to lock the front cover 4 to protect the tape 11. The locking plate 7 is held in this cover closure position under the resilience force of a torsion spring 8 to prevent the front cover 4 from free movement.
On the other hand, when the tape cassette 1 is inserted into a video recorder, the front cover 4 is pivoted and opened in such manner that the tape may be withdrawn as shown in FIG. 2. This is done by pushing a lock release projection 5 of the locking plate 7 by means of a pushing member (not shown) of the recorder in the direction indicated by an arrow C as shown in FIG. 4 against the resilience force of the torsion spring 8 to rock it to the position indicated by broken lines so as to disengage the locking paw 6 from the recess of the lateral plate of the front cover 4 and then the front cover 4 is swinged to the open position shown in FIG. 2.
The spring member 8 is, as shown in FIG. 5, consists of a coiled base portion 8a and a pair of legs 8b and 8c extending straight from this coiled base portion 8a. The coiled base portion 8a is fit on a spring retaining projection 7a of the locking plate 7, one leg 8b is engaged with the surface 7b of the locking plate 7 and the other leg 8c is engaged with a wall 9 of a locking plate housing portion 10 of the lower case 3.
However, the assemblage of the locking plate 7 and the torsion spring 8 into the cassette case is troublesome because it is required to first mount the coiled base portion 8a of the torsion spring 8 on the spring retaining projection 7a of the locking plate 7 and then insert this assembly into position in the cassette.
On the other hand, a V-shaped plate spring was proposed wherein one leg of the spring engages the inner surface of the locking plate and the other leg engages with a wall portion of the lower case so as to normally bias the locking plate (Japanese Utility Model Kokoku No.59-14955). Although this type of spring can be easily assembled into the cassette case, it is not easy to manufacture it into an accurate shape. Moreover, the spring force increases to a large extent with the increase in the rocking angle of the locking plate which exerts an adverse effect on the smooth rocking of the locking plate.